Integrated mid-infrared frequency combs promise to revolutionize chemical sensing. A technologically important approach is to employ a III-V semiconductor in a microresonator-based nonlinear comb. For a comb centered on 4.5 μm, a suitable waveguide material is InGaAs on InP. However, this approach also introduces pronounced higher-order group velocity dispersion that can make it difficult to achieve stable broadband output. One way to stabilize multiple solitons and the repetition rate is to pump simultaneously at two wavelengths separated by one or a few free spectral ranges of the microresonator. Here we show theoretically that this pumping scheme can lead to stable soliton crystals and calculate the required ranges of pump powers and wavelengths. We also show that this stabilization effect occurs only over a limited range of pump power and detuning parameters. For example, for the large detunings needed to isolate soliton pulses, the relative pump power is constrained to rcr⪅P2/P1⪅Rcr with rcr≈40% and Rcr≈97%. The stable parameter ranges are similar for third-order, sixth-order, and all-order dispersion.
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